Voice response units have been developed for generating an acoustic speech signal that communicates an intended message to permit a machine response to a human request for information. The units have been used to automate the process of entering or exchanging information with a system. Thus, voice response units permit natural interactions between a human and a system. The foregoing can be valuable for announcing warnings, reporting machine status or otherwise informing the system user, especially when the human can not view displays, due to concurrent visual tasks, visual handicap, or remote telephone link.
The cellular telephone user responded to the voice response units recorded message by pressing one or more buttons on the keypad of the users cellular telephone. The messages were transmitted to the voice response unit from the cellular telephone in the form of dual tone modulated frequency (DTMF) tones.
Often incorrect information is transmitted to voice response units and entered into the system (as valid data). The incorrect information may result from: incorrectly typed human input information; information that was not heard or understood by the human; or information that was not correctly understood by the voice response unit due to noise on the communications link.
The foregoing problem would be exacerbated by the distance between the cellular telephone and the voice response unit, interference on the cellular network and too many phone calls being made on the cellular network.
The voice response unit and the cellular telephone were also used to calculates a check sum to determine if there is an error in the information transmitted to the voice response unit. The check sum may be the total of the absolute value of the request code, account number, serial number, access code and amount desired to be added to the cellular phone divided by ten. If, the check sum calculated by the voice response unit is not divisible by ten, the voice response unit knew that the information it received was incorrect.
The check sum was used to enable the voice response unit to determine whether or not there was an error in the transmission of the DTMF tones. If, there was an error the voice response unit asked the cellular telephone user to reenter some or all of the previously transmitted information. The cellular telephone user would then at appropriate times press one or more buttons on the keypad of the cellular telephone. The foregoing took some time and was particularly annoying to impatient people. Errors were not also removed by retransmission of the questions and responses, since the same faulty transmission problems may still be present, i.e. the cellular transmission user is transmitting in a area that has a great deal of interference. Reed-Solomon error correction codes have been utilized to correct transmitted data.
The Reed-Solomon Code by itself was incapable of correcting errors introduced in the transmission of data to a VRU. For instance, if a four tone identification code was requested by the VRU and only a three digit identification code was received, the VRU would wait until the fourth tone was received. The fourth tone may never be received.